Studies on late deterioration of renal grafts will be continued with the specific aim of assessing the pathogenic role of immune complexes composed of transplantation antigens and antibodies. Heterophile transplantation antibodies directed against antigens shared by the human nucleated cells and bovine erythrocytes will be further studied and their role in homograft rejection will be investigated. Major emphasis of our studies will be devoted to skin-reactive transplantation antibodies which were discovered in this laboratory. These antibodies are apparently bound to cells and, following reaction with their corresponding antigens, they mediate the release of vasoactive agents. The role of these antibodies in allograft rejection and maternofetal relations will be extensively studied in animals and human clinical material. Further studies on man-mouse hybrid cells will be performed with the major aim of developing procedures which result in genetic repair of an enzymatically deficient cell without interfering with its surface structure. Studies on proliferative lymphocyte responses will be performed in order to further clarify the role of cell cooperation.